1. Field of the Invention
The present invention relates to operating a photoelectric sensor array having photoelectric converter elements and a shutter for controlling the exposure of the converter elements.
2. Background Art
A photoelectric sensor array includes photoelectric converter elements. Each converter element generates an electric signal corresponding to the magnitude of light striking the converter element and the exposure time during which the light strikes converter element. Thus, each converter element forms a single image point or pixel. The converter elements are freely-addressable and readable. As such, the electric signal generated by any particular converter element can be read. Likewise, an electric signal corresponding to the electric signals generated by two or more of any particular converter elements can be generated and read. The exposure of any particular converter element to light striking the converter element may be controlled by a shutter.
Such a sensor array is used, for example, in camera systems in automotive applications that record images of an environment. The recorded images are reproduced, for example, by image analysis responses, or the image sequences are stored. An area of application for such a sensor array is automotive driver assistance systems having different goals such as track recognition or traffic signal recognition.
Typically, the converter elements of a sensor array are associated with groups. The groups of converter elements are allocated to respective imaging tasks. For instance, a first group of converter elements is to receive light from a first light source and a second group of converter elements is to receive light from a second light source. In turn, an electric signal corresponding to the electric signals generated by the first group of converter elements in response to the light from the first light source striking these converter elements is generated and read. Likewise, an electric signal corresponding to the electric signals generated by the second group of converter elements in response to the light from the second light source striking these converter elements is generated and read. As such, each group of converter elements is a targeted partial region or image region of the sensor array. These regions (i.e., regions of interest) are respectively allocated to one of a multiplicity of different tasks or functions. However, these regions may be allocated to different tasks even though the regions are to receive light from the same light source. In any event, in operation, the entire converter elements of the sensor array are reset after each reading process, i.e., the contents of all converter elements are cleared. A problem is that different image regions may sometimes have very different brightness values (i.e., very different electric signals) and this must be taken into consideration for the different functions handled by the image regions.
Known semiconductor sensors can separate the attainable signal deviation of a converter element (i.e., pixel) into partial sections of linear characteristic curves having different slopes. This enables higher order dynamics to be represented through the signal deviation of the pixel. These multiple segmented characteristic curves are valid for the entire image sensor, and limit the attainable signal deviation for each segment of the characteristic.